Table 1. Optimization of reaction conditions ^a .

Entry	Variations from the standard conditions	Yield b
1	None	83%
2	w/o HE	0% c
3	Dark	0%
4	Dark, 80 °C	0% c
5	w/o DABCO	22% c
6	TMEDA, instead of DABCO	43%
7	DBU, instead of DABCO	19%
8	Et3N, instead of DABCO	26%
9	Pyridine, instead of DABCO	19%
10	Cs2CO3, instead of DABCO	21%
11	6, instead of HE	25%
12	7, instead of 4	19%
13	8, instead of 4	25%

^aReaction conditions: styrene 2 (0.1 mmol), 4-cyanopyridine 3 (2.0 equiv.), Togni reagent 4 (1.5 equiv.), Hantzsch ester (HE, 1.5 equiv.), DABCO (1.5 equiv.), MTBE [0.05 M], 90 W blue LED, and rt.

^bYields were determined by ¹⁹F NMR using an internal standard.

^cMajor byproducts determined were dimers of benzylic radicals; see the ESI for details. DABCO: 1,4-diazabicyclo[2.2.2]octane; MTBE: methyl tert-butyl ether.